The present invention relates to a method for equipping papers of value with authenticity features wherein at least one feature substance is applied in the course of papermaking to a moving, wet paper web, in particular a paper web for making papers of value.
Papers of value in the sense of the invention are bank notes, passports, check forms, shares, documents, postage stamps, airplane tickets and the like. The simplified term "antifalsification paper" or "paper of value" used here will therefore always include documents of the stated type.
Such documents of high value must be uncontestably identifiable with respect to their originality and origin because their material value constitutes only a fraction of their commercial value. Identifiability is obtained for instance by special marks used only for proving authenticity. In the ideal case these authenticity marks cannot be imitated, or only with very great effort, and are not falsifiable. Their presence in the intended form therefore guarantees the authenticity of the antifalsification paper. The closer an authenticity feature comes to the ideal of being "not falsifiable" and "not imitable" the greater its value for ensuring authenticity is.
In the past particularly those authenticity features have proven useful which can only be incorporated in the antifalsification paper during production. Such features are e.g. watermarks, safeguarding threads, chemically reacting additives and mottling fibers.
These features are particularly suitable for the visual authenticity testing of antifalsification papers usually performed. Although these features are visually recognizable they guarantee high security because the paper equipped with them can only be produced with elaborate machines to which the forger has no access and whose purchase or construction is not worth it economically for purposes of forgery.
Along with features identifiable visually by the human eye and without aids, antifalsification papers have also been equipped for some time with features identifiable only using special devices With this type of feature the forger has the additional problem of first having to identify the feature or its special properties, whereby identification can be made even more difficult by incorporating the features in the paper solely at precisely defined places.
GB-C 696 673 discloses a method for producing papers of value wherein authenticity features are produced in the form of color patterns within a paper web by injecting a colorant, pigment or ink in solution or suspension into the arising fibrous web in the pulp of a one-cylinder machine at a place where sheet forming has progressed about one half. Direct injection of the feature substances into the pulp, however, exposes them to the currents and eddies present in a rotating cylinder machine. The resulting thorough mingling of the incorporated feature substances with the pulp causes the pulp to be enriched or dyed homogeneously with the injected colorant as time increases, so that the arising paper is finally dyed or provided with feature substances in its total substance.
GB-C 643 430 further discloses a method for producing a paper web provided with a watermark. To produce the possibly colored watermark an endless metal band is guided above the arising paper web of an endless wire machine and moves at the same speed as the arising paper web. The metal band is provided with recesses in the form of the desired watermarks. The diffuse spraying of colorants onto the inner side of the metal band produces the watermark since the colorant can be deposited on the paper web only in the areas of the recesses. This method involves the disadvantage that, firstly, certain shapes can only be applied by templates and, secondly, the colorants are fed to the moist paper web with the aid of solvents so that the paper web is additionally moistened at these places. Altering the water regime, i.e. the addition or release of liquid, can crucially impair the properties of the paper. The local addition of liquid alters the consistency of the paper in these areas so that the location of the applied feature can be detected. Also, for low feature concentrations one cannot ensure that the feature substance is applied in the necessary homogeneous distribution when the feature is applied to the paper with the aid of a liquid as a medium Furthermore, when the colorants are applied with liquid media there is a danger of the fibrous structure of the paper web being visibly changed due to an excessive jet pressure.
Finally DE-C 29 05 441 discloses a method wherein features, such as colorants or chemicals, are incorporated in certain places within a paper web. In a first step a first paper web is produced and the feature substance, dissolved in liquid, applied to one of the surfaces of this paper web using an ink jet printer. In a second method step the side of this first paper web treated with the feature substance is covered with a second, separately produced paper web.